Helping the troubled waters: UW prof and students looking for answers at Thornton Creek

By Steve Hill
University Week

Times have changed at Thornton Creek.

Some 125 years ago the tranquil creek ambled across what is now north Seattle, eventually feeding into Lake Washington. It was perfect salmon habitat. Today, Thornton Creek is all too often a raging torrent, both of water and emotional debate as city officials, homeowners, environmentalists and developers search for a compromise that will please both business and environmental interests.

Logging and development during the past 100 years have dramatically altered the creek. Very few salmon remain, but there is hope. Kristina Hill, an associate professor in landscape architecture, and her graduate students in the urban ecology design studio (LA 504) have spent the fall quarter searching for a way to revitalize the creek. They believe a healthy salmon habitat can be restored one homeowner at a time.

Thornton Creek runs through many residential and commercial areas of north Seattle. At right, Kristina Hill and one of her graduate students talk during a recent charrette about how to revitalize the creek. Photo courtesy of urban ecology design studio

“I think we can get there, but it’s going to take successive iterations,” Hill said recently from her Gould Hall office. “I’m willing to wait 50 years.”

Hill and her students have come up with a variety of small-scale solutions that could be implemented at residences throughout the Thornton Creek watershed. They believe their green-friendly landscaping solutions would be cost effective for the city, agreeable to homeowners and would strike the appropriate balance between business and environment.

“I love controversial subjects,” she said. “As a professional you sort through the heated tone of the debate and develop some insights into what is possible.”

What’s possible at Thornton Creek, she says, is a return to the days when roughly 5 percent of rainfall flowed over the surface and washed into the creek. In the past, much of the rainwater soaked into the sponge-like ground and slowly made its way to the creek. Today, because impervious concrete surfaces like the parking lots surrounding Northgate Shopping Mall have supplanted a conifer forest, about 70 percent of rainfall rushes into the creek right after the rain falls.

“We’re creating flash floods,” she said. “It’s like we’re spraying a fire-hose over the creek bed. It blows out all the habitat, all the places where salmon like to lay their eggs.”

But willing homeowners can make a difference simply by altering the landscape of their yards. By spending $5,000 over a 10-year period, for example, a homeowner could add a number of attractive and effective tools to her yard that would retain rainfall. If the city can be convinced to offset the expensive pricetag with tax-cuts or other incentives to participating homeowners, Hill thinks significant progress could be made.

By adding roof gardens, planting strips, trenches, ponds and cisterns - tanks that retain water during the rainy season and dispense it slowly during the dry season - homeowners can significantly diminish the run-off. Hill and her students are currently performing a sensitivity analysis to determine the amount of water that could be retained if, say, 50 percent of homeowners participated.

In contrast, the city has typically attacked the problem on a larger scale, developing massive holding ponds to retain run-off. That process can be prohibitively expensive and may not accomplish the task of raising water levels in urban creeks during the dry summer months, she says.

“Historically, municipal engineers have taken a centralized approach, thinking from the perspective of managing a complex infrastructure of pipes and ponds,” she said. “They rarely have an opportunity in their work to stop and ask whether private homeowners can do part of the job for them. What we’re saying is ‘Don’t build a big expensive facility. Trust the citizens of the watershed to help you.’ ”

Hill and her students will give a formal presentation of their work on Dec. 6 at 6 p.m. in Gould Hall. That public meeting is expected to draw about 50 people, mostly from the College of Architecture and Urban Planning and Seattle Public Utilities staff, but also creek stewardship volunteers and homeowners from throughout the community who are interested in Thornton Creek.

During that meeting students will introduce their homeowner-based solutions. They will also argue for developing new prototypes in the Thornton Creek watershed to inspire new strategies for urban design, including a pitch for how to most effectively develop a 14-acre parcel of land that currently sits in limbo while haggling over the creek’s future continues.

Students in the class think they’ll be able to make an effective pitch.

“We hope so. That’s our plan, anyway,” said Daniele Spirandelli. “As a group, we’ve come up with a marketing sales pitch that we hope the city could use as a prototype.”

The owner of the 14-acre slab of asphalt just south of Northgate Mall is looking for a buyer willing to pay about $25 million. Many in the Thornton Creek watershed would like to see the city make that purchase and develop a library, a park and a community center on the land. Because it would return much of the area to green space, such a project could also help revitalize the creek. But according to Hill, there’s not enough money in city coffers.

So Hill, her architecture colleague Ellen Do, and their students teamed up to design a variety of prospective developments on the land. Each of their designs included one moneymaking component - everything from commercial real estate to high-density housing. Moneymaking potential is important because it would give the city a partner to help fund purchase of the land and it could bode well for future environmental work in the area.

“For a project to be successful, it has to make money,” Hill said. “Some of that money can then be reinvested into infrastructure and the environment.”

Charrette helps build confidence

Students in Kristina Hill’s regional planning studio recently hosted a charrette - a sort of focused brainstorming session - during which they asked four groups of professionals to develop strategies for retaining moisture throughout the Thornton Creek watershed.

Photo by Steve Hill

The pros, working in groups of three with data prepared by the class, came up with some responses that were very familiar to students. They, too, identified residential areas as potential partners in improving the health of the creek.

“It was flattering,” said Anna Tamura, a student in the class. “We’ve been studying this extensively for almost three months now and it felt like we knew more than they did in terms of design and the whole concept of containing water on individual properties.”

Hill, too, felt the exercise did wonders for the students’ self-esteem.

“Without prompting them, the professionals came up with solutions similar to the ones we talked about during the studio,” Hill said. “I think it really helped the students gain confidence in the value of their own work.”

And because the professionals came from diverse backgrounds - landscape architects, architects, biologists and engineers - Hill’s students were able to examine some interesting group dynamics.

“It was really interesting and useful to see how people from different disciplines interacted in a short, stressful period,” Daniele Spirandelli, another of Hill’s students, said. “They really had to get to the heart of things quickly.”

The students, according to Hill, were able to compare it to an earlier project when the design studio collaborated with building architecture students.

“The landscape architecture students had experienced some intensive interdisciplinary teamwork with students from building architecture earlier in the quarter,” she said. “Some found that it was difficult to work with different disciplines. In the charrette, I think the students learned a lot about how teams work just by getting to be flies on the wall.”